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Rick H Parker

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Reply with quote  #11 

If I use PWM, it means I have to increase PV watt, right?

Right but, your end up with a more durable system. Based on the numbers so far, a 120W - 150w panel is needed.

I learnt that tesla use Panasonic 18650 too?

Telsa used 18650s to get better heat dissipation. Telsa is switching to the lower cost higher density 2170 cells.

As for now, 1 part solved. 24v 30a PWM controller.

That gives us a datum to work from. Have you selected a specific Make/Model or is that still To Be Determined (TBD).

I can get new cells and cost cheaper than deep cycle battery here.

I take it the cell type is finalized. Are you going to spot weld the cells into banks or host them in battery holders? 

All the cells I can get have minimum of 2400mah and maximum 3000mah.

~8 watt-hours per cell for the 2400mah, ~11 watt-hours per cell for the 3000mah. For a 120 cell bank totals would be ~960wh and ~1320wh of storage. 


East Java have very good sunlight.

This is for Surabaya, looks good.

Surabaya Solar Resources.png 



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Rick H Parker
Kansas, USA
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stmbtwle

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Reply with quote  #12 
With the small lithium cells you'll also have to consider the cost/hassle of assembling them into "batteries" but if there's enough difference then it would be worth it. 
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Solar is like the wind. It may be free, but putting it to work isn't!
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Rick H Parker

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Reply with quote  #13 
As for now, 1 part solved. 24v 30a PWM controller.

After reviewing, a 24V 10A is good for panels up to 250W, 30A is good for 750W.  I calculated a 120W - 150W panel will be enough.  We can drop the current rating for the charge controller down to as low as 6A, 6A * 25V charging voltage for a 22.2v bank = 150W.  Using a lower current charge controller will get the cost down. 

eBay prices.
10A li-ion compatible ~$15.00 each.
30A li-ion compatible ~$30.00 each.



Subject to change, still working on details.

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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
colinmcc

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Reply with quote  #14 
I've heard good things about this book, So I just ordered a copy, I'm waiting for it to arrive.

DIY Lithium Batteries: How to Build Your Own Battery Packs

US$15.99 at:

https://www.amazon.com/DIY-Lithium-Batteries-Build-Battery/dp/0989906701/


If you're thinking of building your own packs from 18650 batteries you should find a lot of good help there.
sran

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Reply with quote  #15 
GOD! You guys are helpful! Really appreciate it.

18650 are 3.7v Li-ion cells. He thinking 6 cells per string, 6 * 3.7 = 22.2V. 

AFAIK, 18650 are 4.2v with nominal 3.7v?


He is a lot closer to China then we are. Freight should not be the killer it is for us.  Customs might be a different story.

One of our business involve 1 sea-freight's container (so far) from China. That's why shipping is not a problem.


That gives us a datum to work from. Have you selected a specific Make/Model or is that still To Be Determined (TBD).

I have no idea.


I take it the cell type is finalized. Are you going to spot weld the cells into banks or host them in battery holders? 

Spot weld, fuse each battery.


This is for Surabaya, looks good.

Where did you get that?


With the small lithium cells you'll also have to consider the cost/hassle of assembling them into "batteries" but if there's enough difference then it would be worth it.

No extra cost & time involve. My workers spent hours of their time sleeping/playing games in the office anyway. I let them because they're on standby/on-call, sometimes at night they have to work. Even they're paid extra after work, still I have to make sure they're fit to work at night.
stmbtwle

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Reply with quote  #16 
The reason I suggested the 30a controller was so there would be room to add another panel if needed. That said, the 500w array still has plenty of margin at 1300wh/day. Even a single 250w panel would give you 650wh/day.

If, according to PVWATTS, a 1kw array will produce 89kwh in January (the worst month) that's 2971wh/day. Working backwards from there:
500w = 1486wh
250w = 748wh
200w = 594wh
150w = 446wh
So as Rick said 150w might be enough. Disregard my earlier estimates.

Smaller panels are USUALLY 12v and a 150w panel would have a maximum current of about 9 amps, so a 10a controller would be enough. That same 10a controller could probably handle 250w at 24v.


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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Rick H Parker

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Reply with quote  #17 
AFAIK, 18650 are 4.2v with nominal 3.7v?

In electronics the nominal is the voltage classification. 18650's nominal or classification is 3.7V.  4.2 is the maximum voltage the cell will produce.

Voltage, Nominal: A nominal value assigned to a circuit or system for the purpose of conveniently designating its voltage class (e.g., 120/240 volts, 480Y/277 volts, 600 volts). The actual voltage at which a circuit operates can vary from the nominal within a range that permits satisfactory operation of equipment.


Where did you get that?

I got that image from some modeling software call Homer. The source of the data is the TMY2 and TMY3 data sets provided for free by the US National Renewable Energy Laboratory.

Also  NASA's Surface Solar Energy Data Set.   


It would help if you list the exact make/model of 18650 cells you are considering. Panasonic makes more then one version of the 18650 series, the same can be said for other manufacturers.  Datasheets would be helpful but technical specifications would be better. Like doing a business plan, getting the best balance is in the details. It would also help if you assign a cost and a replacement cost to everything. I can incorporate economics into the modeling.


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Rick H Parker
Kansas, USA
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Rick H Parker

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Reply with quote  #18 
So as Rick said 150w might be enough. Disregard my earlier estimates.

Calculations will get better as my model improves. Right now I am hoping he can provide the information to improve the modeling of the battery bank. The size and performance of the battery bank does effect the required size of the solar panel.

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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
sran

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Reply with quote  #19 
Panasonic ncr18650b
http://www.batteryspace.com/prod-specs/NCR18650B.pdf

For LG, I can't confirm which model yet, as I haven't get the final price.
sran

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Reply with quote  #20 
I forgot to mention, it cost me $1-2 per battery depends on the quantity. (Panasonic)
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